[PLUG] user's mail not being delivered, odd error

[Greg Helledy <gregsonh@gra-inc.com>]

Hi,
We use a VPS to host our company's email, we've been doing that for at 
least five years.  Yesterday for the first time ever, we started having 
a situation where email for one account stopped being delivered.

We use cpanel and the mail queue tool shows a large number of emails for 
that user sitting in a queue to be delivered, but they never are.

When I try to deliver one of the emails in the queue, this output is 
produced:

>  cwd=/usr/local/cpanel/whostmgr/docroot 4 args: exim -v -M 1gyZtM-0006pr-1l
> delivering 1gyZtM-0006pr-1l
>   LMTP<< 220 mail.gra-inc.com Dovecot ready.
>   LMTP>> LHLO mail.gra-inc.com
>   LMTP<< 250-mail.gra-inc.com
>   LMTP<< 250-8BITMIME
>   LMTP<< 250-CHUNKING
>   LMTP<< 250-ENHANCEDSTATUSCODES
>   LMTP<< 250-PIPELINING
>   LMTP<< 250-STARTTLS
>   LMTP<< 250 VRFY
>   LMTP>> MAIL FROM:<68b82096-24c0-11e2-8854-00259069d5fe@bounce.r.groupon.com>
>   LMTP<< 250 2.1.0 OK
>   LMTP>> RCPT TO:<[snip]@gra-inc.com>
>   LMTP<< 451 4.3.0 <[snip]@gra-inc.com> Temporary internal error
>   LMTP>> QUIT
>   LMTP<< 221 2.0.0 Bye
> LOG: MAIN
>   == [snip]@gra-inc.com R=virtual_user T=dovecot_virtual_delivery defer (-44): LMTP error after RCPT TO:<[snip]@gra-inc.com>: 451 4.3.0 <[snip]@gra-inc.com> Temporary internal error

This "temporary internal error" has been going on for well over 24 hours 
now.  Tech support doesn't seem to have much to offer.

They wrote:

> I have checked the issue in detail and could see that the email account, [snip]@gra-inc.com is used as a forwarder email account and confirmed that the issue, T=dovecot_virtual_delivery defer (-44): LMTP error after RCPT TO:[snip]@gra-inc.com: 451 4.3.0 [snip]@gra-inc.com Temporary internal error occurs when an email forwarded to [snip]@gra-inc.com . Please see the following screenshot, [snip]
>
> In order to check the issue in detail can we remove all email on the mail queue, tried to deliver it forcefully. But it is not working.

Note that the account is a regular email account, and the same 
non-delivery occurs whether the email is sent directly to that account 
from outside, or forwarded from another account on our domain.  ALL 
emails are un-delivered.

The VPS is CentOS 7, kernel 3.10, x64.

Anyone run into anything like this?  Is there anything you'd recommend 
for us to do, or tell tech support to do, to fix the issue?

--
Greg Helledy
GRA, Incorporated
P:  +1 215-884-7500
F:  +1 215-884-1385
www.gra.aero
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